This is an open-label, multi-center, industry-sponsored study designed to evaluate the safety and efficacy of Exelon, an acetylcholinesterase inhibitor, in community-based patients with mild to severe Alzheimer's Disease. The study will also evaluate the effect of Exelon on caregiver burden, and utilization of health care resources, and direct and indirect medical costs. One thousand patients will be enrolled in the multi-center study, and seen for 78 weeks. Treatment will begin with doses of Exelon starting at 3 mg/day and escalating 3 mgs/day weekly until the highest tolerated dose (or 12 mg/day) is achieved.